Process for manufacture of shot



Patented Apr. 5, 1938 2,113,279 PROCESS FOR MANUFACTURE OF SHOT John M.Olin, Alton, Ill., and Philip A. Smith,

Hamden, Conn., assignors to Winchester Repeating Arms Company, NewHaven, Conn, a corporation of Maryland Application August 26, 1936,Serial No. 98,080

shot and more particularly to shot formed of lead or lead alloyscontaining no arsenic, or containing a smaller amount of arsenic than iscommonly used in the manufacture of lead shot. Spherical projectiles foruse in fire arms for sportsmens use are commonly called shot. Bymanufacturers, shot is commonly designated either as drop shot or aschilled shot. Drop shot is also sometimes called "soft shot.

Drop shot is manufactured from what essentially is a relatively purealloy of lead and arsenic. This alloy in molten condition is allowed todrip through the perforated bottom of a pan at the top of a shot tower,and after falling through a distance of about 150 feet is collected in awater tank. The molten streams of metal delivered through theperforations in the pan or colander at the top of the tower break upinto globules p 2 of a diameter roughly dependent on the diameterprevent deformation when they strike the water at the bottom of thetower. The main function of the water is to cushion the fall andcomplete the cooling of the metal. The cooled and substantially roundpellets are progressively removed froin the water tank by bucketconveyors, or the like. They are then dried and passed to suitable"sorting equipment where imperfectly shaped pellets are removed. Theyare then graded for size and polished and become the so-called shotgunshot of commerce.

For the so-called drop shot or soft shot, arsenic comprises about 0.1%of the finished projectile. The remaining percentage is lead ofrelatively high commercial purity. If less arsenic is used, the meltedpellets do not form into substantially spherical form as they drop fromthe shot tower pan. Similarly if the lead'is contaminated with usualimpurities, such as tin, or other metals commonly found in scrap lead,the pellets will -not snap into spherical form during the early t-oftheir descent through the air of the shot "to er. 'Nor willthe use ofarsenic correct the j-difllc'ulties when scrap lead is used as the rawmaterial if the impurity is a metal or metals "higher than lead in theelectromotive series,

exceptthe alkali and alkaline earth groups.

v To make the so-called chilled shot, antimony to the extent from about1% to 5% is added to the metal fusion.v It is well known that pellets of55 a lead antimonyalloy areharder than pure lead,

but it has been the practice in the past to use a higher percentage ofarsenic in the manufacture of shot from lead antimony alloys.Commercially pure lead is expensive. Arsenic is expensive.

It is an object of the present invention to provide a method of makingshot for use in sporting fire arms whereby the use of arsenic can begreatly reduced, or even eliminated altogether, and whereby impure orscrap lead can form the major constituent of the shot. Theprocess isapplicable not only to the art ofmaking drop shot, but also to the artof making so-called chilled shot.

By the expression, impure or scrap lead, we here mean such things as oldlead pipe, discarded lead roofing, metal salvaged from worn out storagebatteries, etc. No such materials have heretofore been regarded assuitable for shot making.

' The presence of certain metals in lead alloys, or 20 impurities inlead, prevents the formation of true spheres if the alloy is droppedfrom a shot tower through air, as is the practice in connection withlead-arsenic alloys in the ordinary method of making shot. We have foundthat the presence of very small amounts of metals higher than lead inthe electromotive series, except the alkali and alkaline earth groups,will prevent the formation of true spheres even though arsenic ispresent. Thus, the presence of .0l% tin, .02% cadmium or .05% zincprevents the formation of true spheres. As most scrap lead contains tinin amounts greater than .01 the use of scrap lead in the manufacture ofshot for ammunition has heretofore been impossible and this cheapersource of material has not been used.

We have found that if an inert or reducing atmosphere is employed in theshot tower in place of air and particularly throughout that portion ofthe tower immediately beneath the drip pan where the molten globules arechanging over from a tear-shaped globule to substantially sphericalform, that the presence of metals higher than lead in the electromotiveseries as impurities in the lead does notprevent the formation of truespheres. We have further found that either pure lead or lead containingimpurities of the character set forth can be employed for themanufacture of shot suitable for use in ammunition manufacture withoutthe addition of arsenic if an inert or reducing atmosphere is employedinthe shot tower.

In the accompanying drawing:

Fig. 1 is a somewhat diagrammatic illustration in section of the top ofa shot tower;

Fig. 2 is a sectional view on an enlarged scale, of a portion of oneform of drip pan used in carrying out the process of our invention;

Fig. 3 is a similar view of another form of drip pan; and

Fig. 4 is a similar view of still another form.

As stated above, the shot may be fonned of pellets of lead withoutarsenic and the lead may also contain other metals as impurities. Metalgenerally sold as scrap lead containing various impurities and generallycontaining more than .Ol% of tin may be employed. Such metal can not beused to form shot by the conventional process. By using scrap lead inplace of the commercially pure lead now employed, the cost of the shotcan be materially reduced. Also the use of alloys permits variations ofthe ballistic properties of the finished ammunition to obtain desiredresults.

In making shot from scrap lead or other metal, the apparatus of Fig. 1may be used. In this figure, the floor III at the top of the shot toweris provided with an opening into which loosely fits a skeleton frame llserviceable as a support for the drip pan or colander l2. Frame II alsocan be used as a support for the upper end of cylinder ii. The latter isprovided with an inlet pipe I4 through which an inert orv reducing gascan be supplied to fill cylinder It and maintain the desirednon-oxidizing atmosphere at the perforations in the drip pan. Thediameter of cylinder I3 can be the same as the diameter of the drip pan.Its length is ordinarily dependent on the average size of the pelletsdesired in that particular run of the shot tower. when steam is used asthe inert atmosphere, it can be permitted to escape freely at the bottomof cylinder l3. If illuminating gas, or other combustible gas, issupplied to cylinder [3, it is good practice to ignite it at the loweror open end of cylinder l3, as indicated at It, to avoid developing anexplosive mixture in the shot tower. Steam may be supplied to the towerthrough pipe II, or illuminating gas to be burned at the bottom of thecylinder l3 may be supplied through this pipe.

The shot are collected in a water bath 20 in the usual manner.

As stated above, the invention may be employed in the'manufacture ofshot from impure or scrap lead, either with or without the addition ofarsenic, and preferably without such addition. In carrying out theprocess the molten metal is syphoned from a large fusion kettle througha feed pipe it into the drip pan or colander l2, all in accordance withthe usual practice. The tower I3 is filled with an inert gas and in thepractice of the process we find' that the use of dry steam isadvantageous. We have found that the presence of the steam or otherinert gas in the tower requires the provision of means for preventingthe molten metal from clinging to the drip pan and we accordingly modifythe ordinary construction of drip pan as shown in Figs. 2 to 4. In theform shown in Fig. 2, the pan I2 is formed of aluminum and the openingsin the pan are lined with steel tubes II, the inner and outer surfacesof which are tinned. In using the word "tinned we do not limit ourselvesto the specific metal tin, but use the term common in the art meaningcoating the surface, by the aid of a fiux, with easily fusible moltenmetal such as tin, solder, lead-antimony alloys and the like. Theglobules of molten impure lead or lead alloy drop from the underside ofthe pan and form spheres as illustrated. The tinned surdrop of metalremains in this position until its weight is sufiicient to detach it. Itthen falls through the tower and forms asubstantially uniform sphere.From the above, it will be seen that the outside diameter of the tube.determines the size of the shot.

In the form of the invention shown in Fig. 3 of the drawing, the pan I!may be formed of steel. The openings are lined with tinned tubes similarto those heretofore described but the tubes extend beyond the bottom ofthe pan as indicated at it. This likewise prevents the metal fromspreading over the bottom of the pan and results in the formation ofspheres of substantially uniform size.

In the form of the inventionshown in Fig. 4 of the drawing, the panmaybe made of steel and is first provided with openings of largerdiameter than the intended diameter of the perforations through whichthe molten metal passes. These openings are lined with aluminum bushingsis having openings 'of the desired diameter. The openings in thebushings are formed by drilling holes slightly smaller than the requireddiameter and then drawing a hard steel wire through them until theproper size is obtained. The lower end of the opening is polished andthe burr is removed from the edge. It will be seen that in this form ofthe invention the walls of the openings and the bottom surfaces adjacentthereto are formed of aluminum to which molten lead will not cling orover which it will not spread. This prevents the molten metal fromclinging to the walls of the opening, and results in the formation ofuniform spheres. ents may be resorted to to prevent clinging of themolten metal to the bottom of the pan. A solid aluminum pan, forinstance, may be employed or the walls of the orifices and the adjacentportion of the bottom of the pan may be chromium plated or plated withother metal to which lead or lead alloys do not'have a tendency tocling. The metal drips through the perforations in the bottom of thecolander and immediately'comes in contact with an atmosphere of dryste'am.

Under the above conditions the little streams of molten metal break up.into globules and each globuletakes on a spherical form. This desiredaction is practically instantaneous with pellets of the more usualsizes. For instance, in making #10 shot it is sufficient if cylinder I3is 8 inches long. For shot commonly designated as #2 there areadvantages in having a cylinderv 10 feet long.

A sound scientific explanation of why the desired result is attainedwhen steam is used as the non-oxidizing atmosphere is not easy toformulate. There is the obvious explanation that incipient oxidationdoes not takeplace, and that the perforated bottom of the pan is kepthot,v

not only by the molten metal above, but by the hot steam beneath.- Butaccording to our present ideas, the true explanation is more complex,and centers around certain obscure principles of the laws of surfacetension as applied to a molten metal body falling freely. But whatevermay be the true explanation of the complex principles Various otherexpedi-- cbnimonly used by sportsmen in hunting birds equivalents.

and other small game or for use in trap shooting. f In place of steam,there can be used as the substantially neutral atmosphere such inertgaseous material as nitrogen, carbon dioxide, or their In general, weselect an environment compatible with the needs of the metals and alloysbeing shotted. For impure lead, or for alloys commonly sold as scraplead, steam, nitrogen, or carbon dioxide will serve the purposeadequately. For zinc, or other metal having a strong avidity for oxygen,whether the metal be pure or impure, our process contemplates the use ofa distinctly reducing atmosphere, as hereinafter explained.

Q'According to another embodiment of our processof making shot out ofunusual raw materials, the atmosphere maintained around the pelletsthroughout the initial part of their flight is distinctly reducing incharacter. For instance, we

tower.

"us has been the 'maintenance of a flame at the bottom of cylinder l3,and a complete combustion there of the gas after it is passed throughthe cylinder from the source of supply H. For instance, the metal fusionin the drip pan may consistjo'f zinc of the purity ordinarily found incommercial zinc of high quality, and the protecting atmosphere canconsist of illuminating gas. The resultant finished shot is spherical inshape according to usual shot making practice and the "percentage ofpellets discarded because of irregular shape is not substantially higherthan the percentage discarded in the present lead arsenic practice.Similarly, through use of the process ,h'ereldescribed, scrap zinc ismade available for 'sh making and at costs for raw material far lowerthan those now prevailing in ordinary shot making.

vWhether the initial metal fusion consists essenti ly" of lead, eitherpure or impure, and whether *withfjor without an intentional addition ofarsnio, and whether it consists essentially of zinc, either pure orimpure, the practice of using antimay to give the pellet greaterhardness. is enti'rel'y compatible with the broad principles of our"improved process of shot making. If the fusion consists essentially oflead, pure or,impure, the percentage of antimony added for hardeningpurposes canequal or greatly exceed the percentage now commonly used. Itis possible to ''make the antimony hardened p'ellets'without adding anyarsenic. .'Similarly,if scrap lead be used as the raw material,antimonycan be added in the percentage now commonly used, and even farin excess of those percentages without commercially impairing either thequality or the yield 'of the .finished product.

Arsenic additions to chilled shot of the antimony type play essentiallythe same function as arsenic additions to pure lead shot, that is tosay,.the arsenic has a controlling influence on the spherical shape andconsequently on the percentage of yield from the tower. But according toour invention the use of arsenic as a controlling factor has beensuperseded by the provision of a suitable atmosphere in that part of theshot tower where the'dripping streams are breaking up into globules andwhere those globules are shaping themselves into substantially theirfinal form. This fundamental change in shot making throws open to theuse of the shot manufacturer as rawmaterials a great variety of metalsand alloys not heretofore useful in this art an'd some of them at verymuch less cost than the raw materials heretofore commonly used.

In a copending application we have described more in detail the use ofour process in the manufacture of zincshot and we have pointed outtherein as the salient features of that invention ammunition andelements thereof wherein zinc, or alloys of zinc, with or without theaddition of pellets of other metals or alloys constitute the novelfeatures. a

v While we have referred to the presence of .01% tin, .02% cadmium and.05.% zinc as being a sumcient amount of an impurity to prevent theformation of true spheres by the conventional process, said impuritiesmay be present in much greater amounts when the shot is dropped throughan atmosphere of the type disclosed in this application. Each of thesemetals is higher than lead in the electro-motive series. Onthe otherhand, the presence of impurities consisting of metals lower than lead inthe eleetro-motive series does not have any deleterious effect inpreventing the formation of spherical globules by the conventionalprocess. Thus, the presence of .10% copper or .10% bismuth in anarseniclead alloy produced shot suitable for use in the manufacture ofammunition by the conventional process.

.Some of the metals, higher than lead in the electro-motive series,either do not alloy with lead or, if an alloy is prepared, will notremain in that state at shot dropping temperature. Therefore, in theclaims when we have used the expression alloy of lead and a metal higherthan lead in the electro-motive series, except the alkali and alkalineearth groups, we mean to exclude those metals which will not alloy withlead and remain in that state at shot dropping temperatures.

The metal, magnesium, is sometimes included in the alkaline earth groupand sometimes excluded. In the practice of the present process, itbehaves like members of the alkaline earth group and is intended to beincluded in the group.

The term lead", as used in the claims, is intended to mean commerciallypure lead which does contain small amounts of other metals. Missourisoft lead, for instance, may contain as high as .06% copper but thepresence of copper and other metals lower than lead in the electromotiveseries does not have any deleterious effect in preventing the formationof spherical globules by the conventional process- Commercially purelead, however, does not contain metals higher than lead in theelectromotive series in amounts greater than .01%. The term lead asherein used, therefore. includes these other metals both higherand,lower than lead in the electromotive series in the amounts in whichthey are commonly present.

This application is a continuation in part of alloy of molten lead and ametal hlgher than lead in the electromotive series capable of alloyingwith molten lead, except the alkali and alkaline earth groups, inamounts suiiicient to prevent the formation of spheres in an atmosphereof air, into globules at the top of a shot tower, and maintaining anon-oxidizing atmosphere in the portion of tiliilegtfigwer through whichthe fused alloy starts its 2. The process which comprises separating analloy of molten lead and a metal higher than lead in the electromotiveseries capable of alloying with molten lead, except the alkali andalkaline earth groups, in amounts sufficient to prevent the fofmation ofspheres in an atmosphere of air, into globules at the top of a shottower, and maintaining an atmosphere of inert gas in the portion of thetower through which the fused impure lead starts its flight.

3. The process which comprises introducing molten lead containing as animpurity a metal higher than lead in the electromotive series andcapable of alloying with molten lead, except the alkali and alkalineearth groups, in amounts sufficient to prevent the formation of spheresin an atmosphere of air, into a perforated drip pan arranged at the topof a shot tower, permitting the metal to pass through perforations inthe bottom of the drip pan, and protecting it from contact with oxygenduring at least the initial part of its flight down said shot tower.

4. The process which comprises introducing molten lead containing as animpurity a metal higher than lead in the electromotive series andcapable of alloying with molten lead, except the alkali and alkalineearth groups, in amounts suflicient to prevent the formation of spheresin an atmosphere of air, into a perforated drip pan arranged at the topof a shottower, preventing the metal from spreading on the bottom of thepan, and protecting it from contact with oxygen during at least theinitial part of its flight down said shot tower.

5. The process which comprises separating an alloy of molten lead and ametal higher than lead in the electromotive series capable of alloyingwith molten lead, except the alkali and alkaline earth groups, inamounts suilicient to prevent the formation of spheres in an atmosphereof air, into globules at the top of a shot tower, and maintaining anatmosphere of dry steam in the portion of the tower through which thefused impure lead starts its flight.

6. The process which comprises introducing molten lead containing as animpurity a metal higher than lead in the electromotive series andcapable of alloying with moltenlead, except the alkali and alkalineearth groups. in amounts sufficient to preventthe formation of spheresin an atmosphere of air, into a perforated drip pan arranged at the topof a shot tower, permitting the metal to pass through perforations inthe bottom of the drip pan, and maintaining an atmosphere of dry steamin the portion of the tower throlgh which the fused impure lead startsits high 7. In the process of making shot from molten lead containingasan impurity a metal higher than lead in the electromotive series andcapable of alloying with molten lead, other than the al- .kali andalkaline earth groups. in amounts sufficient to prevent the formation ofspheres in an atmosphere of air; the step which comprises protecting theglobules by a non-oxidizing atmosphere during at least the initialportion of their flight down the shot tower.

shot gun cartridges which comprises separating molten lead containing asan impurity a metal higher than lead in the electromotive series andcapable of alloying with molten lead, other than the alkali and alkalineearth groups, in amounts sufllcient to prevent the formation of spheresin an atmosphere of air, into globules at the top of a shot tower, andprotecting said globules by a non-oxidizing atmosphere during at leastthe initial part of their flight down said shot tower, whereby saidglobules are caused to assume a substantially spherical shape during theinitial part of their flight.

9. The process of making substantially spherical shot'suitable for usein the manufacture of shot gun cartridges which comprises separatingmolten lead containing as an impurity a metal higher than lead in theelectromotive series and capable of alloying with molten lead, otherthan the alkali and alkaline earth groups, in amounts suflicient toprevent the formation of spheres in an atmosphere of air, into aperforated drip pan arranged at the top of a shot tower, permitting themetal to flow through the'perforations into the top of the shot tower toform globules, and protecting said globules by a non-oxidizingatmosphere during the initial part of their flight down said shot tower,whereby said globules are caused to assume a substantially sphericalshape during the initial part of their flight.

10. The process which" comprises separating molten lead containing lessarsenic than is necessary to form spherical globules when lead isdropped through an atmosphere of air, into globules at the top of a shottower, and maintaining a non-oxidizing atmosphere in the portion of thetower through which the globules start their flight. 1

11. The process which comprises separating molten lead containing lessarsenic than is necessary to form spherical globules when lead isdropped through an atmosphere of air, into globules at the top of a shottower, and maintaining an atmosphere of dry steam in the portion of thetower through which the globules start their flight.

12. In the process of making shot from molten lead containing lessarsenic than is necessary to form spherical globules when lead isdropped through an atmosphere'of air, the step which comprisesprotecting the lead globules by a nonoxidizing atmosphere during atleast the initial portion of'their flight down a shot tower.

13. The process of making substantially spherical shot suitable for usein the manufacture of shot gun cartridges which-comprises separatingmolten lead containing less arsenic than is necessary to form sphericalglobules when lead is dropped through an atmosphere of air, intoglobules at the top of a shot tower and protecting said globules by anon-oxidizing atmosphere during at least the initial portion of theirflight down said shot tower whereby said globules are caused molten leadcontaining more than .02 percent of cadmium into globules at the top ofa shot tower, passing the globules down a shot tower, and maintaining anon-oxidizing atmosphere in the portion of the tower through which theglobules start their flight.

16. The process which comprises separating molten lead containing morethan .05 percent of zinc into globules at the top of a shot tower,passing the globules down a shot tower, and maintaining a non-oxidizingatmosphere in the portion of the tower through which the globules starttheir flight.

17. The process which comprises separating molten lead containing morethan .01 percent tin into globules at the top of a shot tower, passingsaid globules down the shot tower and maintaining an atmosphere of drysteam in the portion of the tower through which the globules start theirflight.

18. The process which comprises separating molten lead containing morethan .02 percent cadmium into globules at the top of a shot tower,

passing said globules down the shot tower and maintaining an atmosphereof dry steam in the portion of the tower through which the globulesstart their flight.

19. The process which comprises separating molten lead containing morethan .05 percent zinc into globules at the top of a shot tower, passingsaid globules down the shot tower and maintaining an atmosphere of drysteam in the portion of the tower through which the globules start theirflight.

20. In the process of making shot from molten lead containing more than.01 percent tin, the step which comprises protecting the globules by "anon-oxidizing atmosphere during at least the initial portion of theirflight down a shot tower.

21. In the process of making shot from molten lead containing more than.02 percent cadmium, the step which comprises protecting the globules bya non-oxidizing atmosphere during at least the initial portion of theirflight down a shot tower. v

22. In the process of making shot from molten lead containing more than.05 percent zinc, the step which comprises protecting the globules by a.non-oxidizing atmosphere during at least the initial portion of theirflight down a shot tower.

23. The process of making substantially spherical shot suitable for usein the manufacture of shot gun cartridges which comprises separatingmolten lead containing more than .01 percent tin' into globules at thetop of a shot tower and protecting said globules by a non-oxidizingatmosphere during at least the initial part of their flight down saidshot tower whereby said globules are caused to assume a substantiallyspherical shape during the initial part of their flight.

24. The process of making substantially spherical shot suitable for usein the manufacture of shot gun cartridges which comprises separatingmolten lead containing more than .02 percent cadmium into globules atthe top of a shot tower and protecting said globules by a non-oxidizingatmosphere during at least the initial part of their flight down saidshot tower whereby said globules are caused to assume a substantiallyspherical shape during the initial part oftheir flight.

25. The process of making substantially spherical shot suitable for usein the manufacture of shot gun cartridges which comprises separatingmolten lead containing more than .05 percent zinc into globules at thetop of a shot tower and protecting said globules by a non-oxidizingatmosphere during at least the initial part of their flight down saidshot tower whereby said globules are caused to assume a substantiallyspherical shape during the initial part of their flight.

JOHN M. OLIN. PHILIP A. SMII'H.

